Impact of conventional and biobased microplastics from mulch films on soil bulk density, hydraulic conductivity and water retention in two different soil types under wetting−drying cycles

• 8-month greenhouse experiment revealed differences among effects of microplastics (MP). • No effect of MP on soil bulk density at 0.01 % and 1.0 % in tested soil types. • No effect of MP on hydraulic conductivity at 0.01 % and 1.0 % in tested soil types. • 1 % of starch−based and biodegradable MP increased available water by 5 % in sandy loam soil. The widespread use of plastic products in agriculture, especially plastic mulch films, has raised concerns about the accumulation of microplastic (MP) particles in soils and their potential impacts on the physical properties of the soil, ecosystem health and agricultural productivity and a need for alternatives. This study investigated the effects of conventional, biodegradable and starch−based MP at concentrations of 0.01 % and 1 % (w/w) on selected soil physical properties, namely soil bulk density, saturated hydraulic conductivity and soil water retention. An 8−month greenhouse experiment was conducted under controlled wetting−drying cycles comparing two different soil types. Although the results showed no significant effect on soil bulk density and hydraulic conductivity in either soil type, the addition of 1 % starch-based MP or PBAT (poly(butylene adipate co−terephthalate) significantly increased soil water retention in sandy−loam soils, enhancing water availability by approximately 5 %. However, 1 % LDPE (low−density polyethylene) MP led to a slight reduction in the available water content in silty−clay−loam soil samples. Findings highlight the differential effects of conventional and biodegradable MP on soil water retention, with potential implications for agricultural water management. Environmental relevance: This study examines the impact of conventional and biobased microplastics from mulch films on soil properties over an eight-month period of realistic wetting-drying cycles. By simulating natural conditions, it demonstrates how microplastics alter soil physical properties. The research compares conventional and biodegradable plastics, enhancing our understanding of the risks associated with plastic pollution in agricultural soils, even when biodegradable plastics are used. It also informs sustainable practices by offering insights into how these materials interact with soil environments, highlighting the need for sustainable practices and informing future strategies to mitigate plastic pollution in agricultural settings.